I would make this a bit longer:

"
Naming of getter- and setter-methods for properties follows one of two possible patterns:

Pattern1 for simple-type properties (numeric, string, single entity):
Methods for properties are named as the property, prefixed by their function e.g.  'get' + 'PropertyX' " or 'delete' + 'PropertyX'. Methods that delete entities (referenced as property) are named with 'deletPropertyX', those that just remove the reference to the entities (but do not delete) are named 'removePropertyX'.

Pattern2 for properties that store multiple entities (as vector):
The following methods may exist, where entity is replaced by the actual entities' names: 'Entity getEntity', 'vector getEntities', 'bool hasEntity', 'void addEntity', 'Entity createEntity', 'bool deleteEntity', 'bool removeEntity', 'vector findEntities'.
'getEntity': always exists and is a single entity getter.
'getEntities': always exists and is a multiple entity getter with optional filter parameter.
'hasEntity': must exist if the property is optional, i.e. does not have to be set, may exist otherwise.
'addEntity': exists where references to entities stored in property, adds reference to an existing entity
'createEntity': always exists (entity factory), returns reference to a new entity
'removeEntity': exists where references to entities stored in property, removes reference to an existing entity but does not delete it
'deleteEntity': always exists, deletes entity
'findEntities': exists only for the fiew entities that reference each other internally, e.g. as 'parent' or 'child' and thus build tries. Walks these trees and returns entities matching the given filter.

NOTE: it is important to understand that for the same type of entity 'remove' and 'delete' methods as well as 'add' and 'create' methods may both exist, but mostly not in the same object. Meaning they get added/removed and created/deleted in different contexts.
"

Its a bit long perhaps but I feel it would not be bad to have it, what do you think?